1. Field of the Invention
This invention is directed primarily towards gate valves which are intended for fully closed obstruction of a conduit or fully opened flow.
2. Background of the Invention
Various type of gate valves have been devised in the prior art for use in highly abrasive slurry pipelines such as might be used in the transportation of coal wherein finely ground coal is mixed with water to form a heavy flowable slurry or for the transportation of phosphate ores as mined and pumped from surface mines.
These materials are abrasive and are also contaminated with foreign matter such as small stones and crushed rock, flint and prehistoric animal skeletons. These and like material are very abrasive and tend to erode away the cylindrical portion and gate of gate valves to the extent that the gate valve malfunctions.
The transported material is usually under sufficiently high pressure that the liquid component will seek escape through any crevice.
There have been a great variety of pipeline and valve structures wherein linings of almost every imaginable type have been employed to reduce the rate of pipe line failure due to the abrasive action of the slurry.
Most of the known prior art for resisting abrasion also includes the concept of resisting corrosive material. Butterfly valves are shown in U.S. Pat. No. 3,913,610 and plug valves of exotic metals or liners are illustrated by U.S. Pat. Nos. 3,630,224 and 3,916,943. U.S. Pat. Nos. 3,334,650 and 4,136,709 both disclose valve structures that include abrasion resistant liners. However, both of these patents refer to ball valve structures and make no reference to the application of abrasive and chemical resistant liners for slurry gate valves. Due to the high cost of manufacture of slurry gate valves and more importantly because of the extremely high cost of replacing the same, a need has existed in the art for a slurry gate valve of improved reliability. Replacement or repair of a slurry gate valve necessitates down time in a commercial operation while the faulty valve is pulled out of line either for repair or replacement of the same. Therefore, it is the primary object of this invention to provide a slurry gate valve that overcomes the aforementioned inadequacies of the prior art gate valves and provides an improvement which significantly contributes to the ease with which such a gate valve can be manufactured and repaired.
A further object of the present invention is the provision of an improved seal for a gate valve for which seal may be readily replaced or repaired on location.
Another object of the invention is the provision of an improved interfit which is accomplished by using an abrasive resistant lining insert in a dual function. Firstly, the lining is a tubular insert for improved construction and secondly the lining defines a gate sealing and receiving slot.
Another object of this invention is to provide a slurry gate valve in which the cylindrical conduit portion includes a sleeve liner of abrasion resistant material.
Another object of this invention is the provision of a slurry gate valve in which resinous sealant sealingly engages the entire periphery of the gate when the gate is in the first or closed position.
Another object of the present invention is the provision of a transparent cover for the top portion of the stem to prevent the egress of deleterious matter within the gate driving means and to indicate the position of the gate.
Another object of the present invention is the provision of a gate of highly abrasive-resistant alloy.
Another object of the present invention is the provision of an annular channel and adjacent undercut key portion disposed within each sleeve liner for an annular wiping seal which sealingly engages an adjacent surface of the gate.
Another object of the invention is the provision of a method of forming an annular wiping seal within each sleeve liner in which a mold is positioned adjacent to the inward face of the sleeve liner and a resinous sealant is poured through an annular passage of the mold into the annular channel and key portion to cure therein.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Particularly with regard to the use of the invention described herein, this should not be construed as limited to slurry gate valves but should include all gate valves and the like.